Definitions:
an agriculturalist, specifically a student at an agricultural college. frequently (and in earliest use): a member of a sports team from such a college; (in plural) the team itself.

an agricultural institution or college (often as the nickname of a specific institution).

of or belonging to an aggy or aggies; relating to an agricultural college, department, team, etc.

a type of highly-prized playing marble made of agate or variegated glass resembling agate.